Any good ideas for my 18th Birthday?

I want to leave the state for my 18th Birthday. Its going to be me and my son, and possibly my boyfriend. I really want to go where theres a beach and the ocean. I was thinking California or Maine (I love seafood!) but I need something somewhat cheap. Like possibly nothing over $1,000. I don't know, I'm willing to bend it a bit. I only want to go for 4 or 5 days. I was thinking a cruise but I was a little iffy with my son only being 21 months at the time. Also a good airline to find cheap tickets. Thankfully my son will be under 2 so his ticket should be free, cause he'll be in my lap. Any good restaurants, cheap hotels, ect, would help A LOT!! Just someplace that I can enjoy and where my son can also have fun. Thanks :)